Which of the following elements have two electrons in their electron-dot structures?

i thought it was just barium and calcium but apparently i was wronghow did you figure it out? i thought that all i would have to do is see which elements are in group 2 and that gives you the number of valence electrons so what did i do wrong?1 aluminum2 barium3 cobalt4 lithium5 bromine6 helium7 krypton8 calcium9hydrogen